var i = 1;
function go() {
    var num =parseInt(Math.random()*14+1)*14;
    var timer=setInterval(function () {
        num--;
        if (num==0) {clearInterval(timer);
        }
        var items=document.getElementsByClassName('item');
        for (var item of items){
            item.classList.remove('active');
        }  
        var item=document.getElementById('item'+i);
        item.classList.add('active');
        i++;
        if(i>14){
            i=1;
        }
        },100);
    }